docs: move architecture map into docs/ and refresh it against the live tree

The architecture/code map previously lived in .claude/CLAUDE.md, which was
gitignored (local-only) and auto-loaded into every agent session alongside
the root CLAUDE.md. Track it in docs/architecture.md instead and reference
it from CLAUDE.md so it is read on demand.

While moving it, fact-check the whole map against the current tree:
- add the missing internal/eventbus and internal/tunnelmonitor packages,
  the service/email subpackage, and util/wirecodec
- document node mTLS (tls_client.go, node_mtls.go, setting_mtls.go) and the
  fourth TLS verify mode
- add the Host, ClientExternalLink, NodeClientIp and ClientGlobalTraffic
  models plus their symptom-index rows
- correct the cron table (check_cpu_usage is 1m not 10s; add
  check_memory_usage and free_os_memory), the middleware chain
  (MaxBodyBytes, ConfigEnvelope, CSRF) and the controller route prefixes
- refresh the sub/ and service/ file listings, frontend pages (hosts/,
  index/), CI workflow list, and replace stale exact line counts with
  rounded sizes

CLAUDE.md

@@ -3,6 +3,9 @@
 Operational guide for AI agents working in this repo. Long-form human docs:
 `CONTRIBUTING.md` (setup, testing philosophy) and `frontend/README.md`.
 Read those before large changes. This file is the short, must-follow version.
+For a deep navigation map (request lifecycle, cron-job table, symptom → file
+index, layering rules), read `docs/architecture.md` on demand — do not guess
+file locations when it can answer in one hop.
 
 ## Stack
 - Backend: Go 1.26 (`module github.com/mhsanaei/3x-ui/v3`), Gin, GORM.